If tan−1x+tan−1y=4π, xy<1, then write the value of x+y+xy.Answer: 1SolutionSince xy<1, tan−1x+tan−1y=tan−11−xyx+y. Thustan−11−xyx+y=4π ⇒ 1−xyx+y=tan4π=1x+y=1−xy ⇒ x+y+xy=11CBSE Class 12 Board · 2014 · Subjective